The invention relates to a valve-controlled internal combustion engine.
U.S. Pat. No. 4,617,881 describes an internal combustion engine having a group of three inlet valves and another group of two exhaust valves per cylinder. The valves are arranged around a spark plug provided centrally in the combustion chamber. In order to obtain an optimum arrangement of the valves in the combustion chamber, these valves are fitted at an incline relative to a center longitudinal plane running through the row of cylinder bores. In this known arrangement, the center inlet valve of the three inlet valves has a greater inclination than the two outer inlet valves. As a consequence thereof, the valve-stem end of the center inlet valve in the cylinder head is relatively far away from the center longitudinal plane. Since the center inlet valve is actuated via a bucket tappet, the camshaft controlling the inlet valves must consequently run above the bucket tappet of the center valve. This results in the camshaft axis having to be arranged relatively far to the outside in the cylinder head, as a result of which the width of the cylinder head increases undesirably. Since the outer inlet valves of the valve group are arranged at a less pronounced incline relative to the center valve, their distance from the camshaft in turn inevitably increases and longer rocker arms are required to actuate them. Due to this fact, the mass in the valve-operating gear increases disadvantageously and unavoidable elasticities occur in the valve-operating gear due to longer arms. A further disadvantage is that different cam contours are necessary to obtain an identical valve stroke for all inlet valves of a valve group by the control of the valves on the one hand directly via bucket tappets and on the other hand via rocker arms, as a result of which the manufacture of the camshaft becomes more expensive. In valve-operating gear of this type, the multiplicity of parts increases disadvantageously due to the use of bucket tappets and rocker arms.
An object of the present invention in a valve-controlled internal combustion engine of the type having first and second valve groups is, therefore, to create valve-operating gear which, while retaining a favorable valve arrangement in the combustion chamber, permits a simple arrangement of the components of the valve-operating gear in the cylinder head while requiring few parts. Another object is to provide such valve-operating gear which occupies only a small amount of space in the cylinder head.
Such objects have been achieved according to the present invention by arranging the axes of one valve group at an approximately some distance from a longitudinal axis of the associated camshaft, and mounting rocker arms for the valves of that valve group alternately on either side of the camshaft at approximately the same distance from the latter.
A valve-controlled internal combustion engine has in accordance with the present invention for each cylinder a first valve group consisting of three inlet valves as well as a second valve group consisting of at least one exhaust valve. The valve axis of the valve group is inclined relative to the axes of the other valves of that group so that the end of the valve stem of this group, is at a different distance from an imaginary center longitudinal plane running through the row of cylinder bores of the internal combustion engine. A camshaft for controlling the valves of the first valve group of the cylinders runs with its longitudinal axis above the valve-stem ends at approximately the same distance from the valve axes. Cams arranged on this camshaft, via rocker arms which are in contact at their free end with the valve-stem end, actuate the valve allocated to each of the rocker arms. The rocker arms of the valve group, at their other end, are mounted alternately on either side of the camshaft at approximately the same distance from the camshaft.
By virtue of this arrangement, the width of the cylinder head can be reduced, and, to reduce the multiplicity of parts, all valves of the group are actuated via rocker arms of the same type. The length of the rocker arms is limited and a reduction in the masses as well as in the elasticities is thereby achieved. In addition, the roof shaped design of the combustion chamber and thus a favorable combustion-chamber form can be retained.